Abstract: Objective To investigate the proper inner control genes suitable for mRNA expression level comparison of aging rat tissues. Methods Real-time reverse transcription PCR was used to examine in aging rat tissues the expression level of G3pd（glyceraldehyde-3-phosphate dehydrogenase）,ACTB(?-actin),H3f3b（H3 histone, family 3B）,Arbp（acidic ribosomal phosphoprotein P0）and 18S(18S ribosomal RNA ).Results The most stably expressed housekeeping gene in aging rat kidney was ACTB, as for heart and lung G3pd showed the minimum variation; Arbp expression was the most stable among different tissues. Conclusion For aging rat intra-tissue mRNA normalization at least two housekeeping genes should be used: one is the ribosomal RNA gene 18S and the other suitable control gene is Arbp.

Key words: reference genes, HKG, mRNA normalization, real-time RT-PCR